Method of making ingot mold plugs



Nov. 12, 1940. c. ESTEP 2,221,130

' METHOD OF MAKING INGO T MOLD PLUGS Original Filed Sept. 3, 1937 A 770RNA-'75.

Patented Nov. 12, 1940 UNITED :STATES PATE T OFFICE 2,221,130 METHOD orMAKING moor MOLD PLUGS Original application Septemberfi, 1937, SerialNo. 162,315- Renewed May 25., 1939. I Divided and this application June24, 1939, Serial No. 281,002.

3 Claims. (o1. 22-193) This invention relates to a method of makingingot mold plugs and more particularly to a ceramic or a refractoryingot mold plug particularly adapted for advantageous use with abigend-up ingot mold. The instant application constitutes a division ofmy prior- Patent No. 2,170,555 filed September 3, 1937, allowed June 9,1938, and renewed May 25, 1939, renewal Serial No. 162,315.

v In the art of casting ingots there has been a general adoption of thebig-end-up type of ingot mold; that is, a mold having an open top withside walls gradually diverging from the bottom toward the top. A taperedhole is provided at the bottom of the mold which is closed by a sealing.plug While the ingot is poured and the ingot, after cooling, is forcedupwardly out. of the mold. Prior to pouring the ingot the plug referredto is forced into the hole at the bottom crushing or abrasion againstthe wall of the hole, an ingot mold plug formed of burned clay iscapable of effecting an efiicient sea The pres- 30 ent invention relatesprincipally to the method of making refractory ingot mold plugs, thelatter bein particularly described and claimed in my aforesaidco-pending application.

It is among the objects of my invention to pro- 35 vide a burned clayingot mold 'plug and method of making the same whereby the plug willwith- .deaerating of the extruded mass.

extruded clay tile cylinder is upset to form a plug having a truncatedcone shape. It is a further object of my invention to provide a burnedclay mold plug characterized by smooth troweled outer surfacesespecially resistant to spawling 6' and cracking. It is also among theobjects of my invention to provide a method for making a mold plug inaccordance with the preceding object. Further objects and advantagesrelating to economies of manufacture and characteristics of the 10finished mold plug will appear from the following description and theappended drawing in which- Figure 1 is aview of a clay extrusionapparatus suited to extrude laminated cylindrical stock employed in myinvention; 5

Figure 2 is a sectional view with parts broken away of an upsetting ormolding apparatus made according to my inventio Figure 3 is anenlargedsectional view of the relief mechanism employed in the upsettingor molding apparatus; I

Figure 4 is a transverse sectional view (taken 'alongthe line 44 ofFigure 5) of a mold plug constructed according to my invention;

. Figure 5 is a plan view of the mold plug; '25

Figure 6 is a partial sectional showing of a mold plug according to myinvention arranged within an ingot mold.

The first step in forming a mold plug corresponding generally to theobjectsoutlined above comprises extruding wet clay stock of round crosssection such as 4 inFigure 1. Preferably the clay stock is extruded froman anger machine 5 of the type in which the mass of wet clay beingextruded is open. to the atmosphere through a hopper as at 8 tofacilitate the formation of laminations in the extruded stock 4. Thereis a tendency for extruded clay products to form laminations generallyparallel to the walls of the extrusion die and in forming certainarticles it is conventional practice to extrude from a chambermaintained at less than atmosphere pressure to prevent the formation oflaminations. According to my invention, however, I prefer to takeadvantage of the laminating tendency referred to and therefore preferthat there be little or no In addition to insuring against deaeratingthe mix should be sufficiently short so that marked circular concentriclaminations coaxial of the stock will be formed in portion 4. The claymay be fed to the auger machine 5 from a pug mill 7 in the usual mannerand forced "by an auger through the forming throat l3 and extrusion diel2. The extruded stock 4 is severed by Wire cuttersor Figure 2 acylindrical mold plug other suitable means into short cylindrical slugs6 having a volume corresponding substantially to the volume of afinished mold plug.

Subsequent to the extrusion of the clay stock 4 and the cutting thereofto provide cylindrical slugs 6, the slugs are each transferred while ina plastic condition to an upsetting apparatus arranged to upset thecylindrical slug into a plug having a truncated cone shape. In Figure 2I have illustrated a preferred form of upsetting apparatus in which apair of cylindrical bores l9 and 26 are joined to each other by atapered wall portion 2| which corresponds substantially to the shape ofthe finished mold plug. A backup or ejector plunger 24 is positionedwithin the bore chamber and the upsetting plunger 26 is arranged withinthe bore 20 so that it may be moved to close the opposite side of themold plug chamber. I have shown in the dotted lines of blank 6 aspositioned prior to its upsetting and the upset mold plug 30 resultingfrom the movement of the plunger 26 to its position shown fills the moldplug chamber.

I have found that by upsetting a cylindrical clay slug as abovedescribed that the exterior surface of the article is improved by theformation of a hard, tough spawl-resistant cover. The pressure upon thewet clay slug appears to bring moisture to the outer surface of theupset article and upon burning a thin cover or skin is formed which isresistant to spawling. .The spawl resistant covering resulting fromupsetting the slug as above described may be further improved byeffecting a troweling action upon the outer surface of the slug duringand/or after the upsetting. The troweling or wiping of the outer surfaceis preferably accomplished by rotating the plunger 26 and such rotationis preferably effected so as to effect no disturbance of the 1aminatedstructure within the body of the plug. The rotation of the plunger 26may be accomplished by having the plunger shaft splined axially as at 43so that the shaft may reciprocate within an internally splined worm gear4| supported by a bracket 40. A spur gear 42 is arranged to mesh withand drive the worm gear 4|. The rotation of the plunger 26 during and/orafter the upsetting of the slug appears to effect a troweling of thesurface which forces water and minute clay particles to the outersurface of the plug. Upon burning the smooth troweled outer surface ofthe plug acquires a hard, tough, skin-like cover which is resistant tospawling and thus contributes to the prevention of nonmetallics beingcarried up into the ingot during the pouring thereof.

Due to the fact that as a practical matter in commercial production itis difficult or impossible to obtain a series of cylindrical slugs 6which are of exactly the same volume and due to the fact that suchplastic slugs are more or less incompressible, it would, in the absenceof an apparatus such as I have provided, be difficult to obtain moldplugs completely shaped and filled. Because of the variation in volumeof the cylindrical slugs and because it is desired to produce truncatedcone shaped mold plugs of uniform height and full body, I have providedan upsetting apparatus which will compensate for the normal variationsin the volume of the cylindrical slugs.

Preferably the back-up or ejector plunger 24 is l9 to close the lowerend of the upsetting centrally apertured as at 25 (Figure 3) and carriesin said aperture a piercing tool 21 which is normally urged upwardly tothe limit of a slot such as 28 by a spring 29. Each of the cylindricalslugs 6 is initially cut so as to provide a volume 5 of material lessthan the volume of the space between the two plungers 24 and 26. Whenthe plastic slug 6 is forced downwardly into the upsetting chamberdefined by the two plungers and the tapered wall 21, it will be observedthat the piercing tool 21 is forced into the plastic mass and that theplastic slug offers a resistance to the movement of the plunger 26 untilit has reached the end of the cylindrical bore 26 as shown. As theplunger 26 approaches the position shown it will be understood that thehydrostatic pressure in the slug being upset will force the piercingtool 21 downwardly out of the upsetting chamber against the resistanceof the spring 29. The distance which the piercing tool is forceddownwardly out of the upsetting chamber by the hydrostatic pressure intheplastic slug will depend upon the difference in volume between thecylindrical slug and the volume defined by the tapered wall 2| and theplungers 24 and 26 in their positions shown in Figure 2. It is possibleaccording to the known methods of cutting plastic clay stock to cutcylindrical slugs in which the volumes will not vary with respect toeach other more than the volume of the piercing tool 21 in its raisedposition. Thus it is possible with the usual known methods of wirecutting wet clay stock and the method and apparatus I have provided forupsetting such stock to obtain mold plugs having a truncated cone shapeand having a uniform height and otherwise being uniform in theirexternal dimensions. 1 Y

The steps which include the cutting and up- 4. setting of the plasticclay blank are preferably carried out in a manner which will notappreciably disturb the cylindrical laminations in the slug so that thefinished upset plug will in effect comprise a series of tapered tubesmore or less {$5 distinguishable from each other by laminations such as16 shown in Figure 4. Subsequent to the upsetting as described inconnection with Figures 2 and 3 the plastic mold plug is burned in theconventional manner and the resulting (50 laminated upset and burnedplug 32 is shown in Figures 4 and 5.

The finished plug may be inserted through the open end of an ingot mold35 and driven into the base of the ingotmold to close the opening L5? 36therein as shown in Figure 6. Ordinarily an ingot mold plug of this typeis forcibly wedged into the opening 36 by driving and jarring operationseffected with a heavy timber or the like reciprocated from the open endof the ingot mold. Q9 The impact at the upper surface of the plug may besufficient to effect a slight abrasion or surface fracture of theconical walls of the ceramic mold plug so that the plug will acquiresubstantially the shape of the aperture 26 to which it is fitted I5tight seal against the molten metal and form a poured into the mold.

It will be observed that even though the impact of a heavy timber suchas is required to force the plug into the mold opening 26 be such @713as would break or fracture the plug, the truncated laminations definedby surfaces l6 tend to permit the plug sections between said surface toslip with respect to each other. It is possible that a mold plug of myinvention could be 75 driven into the opening 36 with such force thatthe plug is fractured two or three times on different concentric conicalsurfaces [6 and yet its utility as a mold plug will be preserved. Itwill also be understood that such plug fracture caused by internalstresses within the plug growing out less of the cause of plug fracturethe usefulness of the plug is not destroyed as long as the fracture isrestricted to concentric surfaces such as It. desirable characteristicsof a broken or spawled particles of the plug and carry the same up intothe ingot. An ingot carrying particles of non-metallic is obviouslydefective for rolling purposes. It will be observed that due Although Ihave illustrated and described certain specific forms in which myinvention may be practiced, various changes and modifications will occurto those skilled in the art, all within the precepts of my invention,and I do not care to be limited to the precise embodiments hereinparticularly described or in any manner other may be entitled Iclaim: 1. That method of making an ingot mold plug which comprisesextruding a length of clay stock which comprises extruding clay stock,cutting said stock transversely to produce blanks proportioned intoconically surfaced plugs by compressing said blanks in the direction ofextrusion and burning said plugs,

3. That method

